package days48;

import java.util.Scanner;

public class day34 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        while (scanner.hasNext()) {
            long a=1;
            long b=1;
            long c=0;
            long from=scanner.nextInt();
            long to=scanner.nextInt();
            long sum=0;
            for (int i = 1; i <= to; i++) {
                c=a+b;
                if(i>=from){
                    sum+=a;
                }
                a=b;
                b=c;
            }
            System.out.println(sum);
        }
    }
}
